Powered actuator systems have a variety of usages in aircraft or aerospace applications, such as to actuate control surfaces, doors, foldable wings and the like.
One type of power driven actuator system utilizes a planetary gear train having one or more planetary gear sets. Often, the outer ring gear or gears of the planetary gear train are coupled directly to the actuator arms for the control surface, door, foldable wing and the like. Most often, at least a pair of actuator arms are used to actuate or move the control surfaces for a variety of reasons, but if for no other reason than to rigidify the surface and provide for uniform movement. Therefore, the actuator arms often are asymmetrical in both a radial direction and an axial direction of the planetary gear set. In fact, the actuator arms may not even be of the same size.
Typically, particularly where identical actuator arms can be used, the arms are constructed of a one-piece construction, such as of forged steel, and the respective ring gear is formed integrally therewith as an internal ring gear portion at one end of the arm. However, where asymmetrical arms are used, and particularly in actuator systems in aerospace applications, various problems result from this typical construction. For instance, where such left and right-hand parts are used, machining and overall processing adds manufacturing and inventory costs. In addition to the cost factor, unnecessary strength and weight associated with an integral all-steel construction of the actuator arms is undesirable in aerospace applications where size and weight parameters are critical. In other words, hardened steel may be necessary for the ring gear and its associated bearing race, but such strength requirements and resulting excessive weight is unnecessary for the entire actuator arm construction and very undesirable in aerospace applications.
Another problem with the typical one-piece construction involves distortion resulting from heat treatment. Due to the size and varied cross section of most actuator arms, a one-piece construction, involving heat treatment to harden the steel for the gear portion, would add operations to straighten, remachine and realign the actuator arm portion following heat treatment.
Consequently, it is more desirable, particularly in aerospace applications, to have an actuator system wherein the driving ring gears and the actuator arms are separate components. The ring gears thereby can be fabricated of hardened steel and the actuator arms can be fabricated of lightweight material, such as forged aluminum. However, such a two-piece construction then creates its own problem of requiring excessive inventory because of the typical asymmetrical or "right and left-hand" nature of most actuator arms. This again gets back to the manufacturing and inventory cost dilemma.
This invention is directed to solving these problems by providing an actuator system of a "universal" type wherein common or universal ring gears are used in conjunction with asymmetrical actuator arms in such a manner that the actuator arms can be mounted in alternative positions on the universal ring gears and thereby require only one ring gear construction and one asymmetrical actuator arm construction, but interchangeably positioning the ring gears and actuator arms at plural positions in the actuator system.